Has anyone had an issue where nlapiLookupField on a purchase order record only returns null in a SuiteScript model?

I'd suspect almost certainly a permissions issue. Are you doing this in a service file with elevated permissions?

I do have elevated permission. I'm also using the same service to load the purchase order record in another model function.

Tried the 4th input parameter as true?

I have not tried the 4th param.

Is it definitely a body field?

it's the total field, which is listed on the PO records browser search fields.

Does it return OK from console in UI?

it does return no problem

I've had occasional issues with nlapiLookupField in SSPs returning unexpected values. In one case, it was returning an entirely different field value. I'd try switching to a search instead. Speed overhead's not generally an issue with small record counts

@Kearobi please make sure the permission for purchase order to view